\documentclass{article}
\usepackage{stackengine}
\newcommand\xrowht[2][0]{\addstackgap[.5\dimexpr#2\relax]{\vphantom{#1}}}
\begin{document}
	\begin{table}[h]
		\centering
		\begin{tabular}{|c|l|}
			\hline
			col1 & col2 \\
			\hline\xrowht[()]{10pt}
			1 & 2g \\
			\hline\xrowht{20pt}
			3 & 4 \\
			\hline\xrowht{30pt}
			5 & 6 \\
			\hline\xrowht{40pt}
			7 & 8 \\
			\hline
		\end{tabular}
	\end{table}
\end{document}
